The invention relates generally to a method for manufacturing a semiconductor device and, more specifically, to a method for manufacturing a transistor including a multi channel.
Generally, a semiconductor manufacturing process includes fabrication, electric die sorting, assembly, and testing. The fabrication includes repeating diffusion, photo-resist patterning, etching, and deposition over a wafer several times to form electric circuits, thereby obtaining semi-finished products that can be electrically operated upon in a wafer phase.
As the critical dimension (CD) of a gate decreases in size due to the high degree of integration of semiconductor devices, channel length is reduced, thereby causing a short channel effect (SCE) where an electrical characteristic of a field effect transistor (FET) is degraded.
In order to prevent the degradation of the electrical characteristic, there has been suggested transistor that includes a recessed gate and a channel region having a three-dimensional, rather than a two-dimensional, structure. The channel length denotes a distance between a source and a drain of the transistor. The recessed gate formed in a trench generated from a process of etching a semiconductor substrate by a predetermined depth, not formed on a top surface of the semiconductor substrate, can increase a channel length because the channel region is formed along walls of the trench.
Recently, semiconductor devices designed to reduce power consumption with high integration have been required. Particularly, for reduction of power consumption, the amount of leakage or consumed current due to resistance and capacitance in the semiconductor device should be decreased so that a driving current is consumed most effectively while the semiconductor device is operated. In order to effectively consume the driving current, it has been suggested that a transistor may include a double gate structure, where double gates are respectively positioned on sides of a channel region, as opposed to in the center of the channel region.
As an example of the transistor including the double gate structure, there is a transistor including a fin gate that surrounds a fin-shaped channel region. The fin gate improves a driving capacity of gate of the transistor so as to make the driving current use in the semiconductor device effectively and, notwithstanding a narrow width of the fin-shaped channel region, substantially increases a channel length between a source and a drain of the transistor so as to prevent the SCE. That is, according to a potential of the fin gate, an active region, i.e., a channel, in the fin-shaped channel region is formed in a bent shape along a contact surface between the fin gate and the fin-shaped channel region, thereby increasing a driving capacity of the gate and improving an efficiency of electricity.
Further, to prohibit a transistor included in a highly integrated semiconductor device from the SCE, a transistor including a recessed gate has been suggested. Unlike a conventional transistor, the recessed gate is formed at lower level than source/drain of the transistor. The source and the drain are formed on top of the substrate, and the recessed gate is formed in a lower part of a trench between the source/drain of the substrate. As a depth of the trench is deeper and a depth of the source/drain is shallower, a channel length of the transistor is longer.
Meanwhile, a semiconductor device with a high degree of integration is required to operate at high speed. For meeting a high operation speed, a multi-channel Field Effect Transistor (FET) including plural channels has been suggested. Because, through the plural channels, movement of carriers between source and drain is facilitated, speed of operation of the transistor can increase. In addition, when the transistor includes a multi-channel, a driving current capability of the transistor is also improved.
As above described, a semiconductor device qualified in views of integration, speed, and power consumption should have advantages of a fin-shaped gate, a recessed gate, and a multi-channel. However, it is difficult to form a fine multi-channel of the semiconductor device over a semiconductor substrate through photolithography with a photo-resist pattern. Also, because of reduction of design rules, it is easy to cause short between neighboring source and drain regions when active regions of source and drain corresponding to the fine gate pattern is grown by a silicon epitaxial growth (SEG) method.